This disclosure pertains to an aqueous inkjet ink, in particular to an aqueous inkjet ink comprising an aqueous vehicle, a dispersed pigment colorant, a dispersed polyurethane polymer, and a dispersed olefin ionic copolymer.
Inkjet printing is a non-impact printing process in which droplets of ink are deposited on a substrate, such as paper, to form the desired image. Inkjet printers are equipped with an ink set which, for full color printing, typically comprises a cyan, magenta and yellow ink (CNN). An ink set also commonly comprises a black ink (CMYK).
During inkjet printing, it is often necessary for the recently printed-article to come into contact with the paper-handling mechanism of the printer, e.g., in the case of duplex printing where both sides of the media are printed. In this case the first printed side may not yet be completely dry and as a result the print surface can be damaged and the ink can transfer onto the paper-handling mechanism and then onto subsequent prints. This problem is particularly acute when using a wet-press which involves considerable paper-handling at high speeds. Often the press uses heated rollers to transfer media which is prone to having problems as the drying ink sticks to the rollers. Severe problems may be encountered when slow-drying inks are printed onto non-absorbent media such as coated offset media.
U.S. Patent Application Publication No. 20080269374 discloses the formation of a passivation layer on pigment surface to prevent pigment-latex separation when applied to a substrate so as to improve durability. JP11001563, JP08239605 and JP08231909 disclose ink compositions containing ethylene/acrylic acid copolymer.
A need still exists for inkjet ink formulations that provide good short-term print durability. The present disclosure satisfies this need by providing ink compositions containing dispersed polyurethane and dispersed olefin ionic copolymer having improved durability.